what's the difference between a simple microphone and a active microphone

Professional series microphones require power for them to work.

http://en.wikipedia.org/wiki/Phantom_power

http://en.wikipedia.org/wiki/Condenser_microphone#Condenser.2C_capacitor_or_electrostatic_microphones

http://www.mackie.com/pdf/arcane_mysteries.pdf

Inexpensive microphones do not need power. The microphone sends the audio signal to a device such as an amplifier, tape deck, digital recorder, mixer, and other devices.

Here is a DVR microphone that requires 12 volts dc to operate.
http://eclipsecctv.com/ECL-MIC_microphone.html


What is it that you are trying to do?

my 8ch mpeg dvr has 4 input audio and 2 out put. what do I plug into them so I can have audio with my video . How are these used. I have cameras on the out side of my house and I would like to here what is going on as I view the video live and capture audio on the video. what do I need to buy?

You are best to hire someone local to you!

ICR150<------------------------------<power
ICR150>------------------------------>DVR Audio IN

http://icrealtime.com/solutions/cameras.asp?cameraid=ICR150

It has a built in audio microphone, easy top or bottom mount as well as a removable sun shield. The ICR IR150 comes with a SONY 1/3 inch high resolution sensor that provides 480 lines of resolution. It comes with a 3.6mm (optional 4mm, 8mm, 12mm) fixed lens

Be prepared to get arrested if you are not familiar with recording laws. You will soon be educated more then you wish.

I can stick a cam corder with no audio up the bottom of a dressing room wall, and it is only a misdemeanor, and the cop will ROR me (release on own recognizance).

http://scorpiontheater.com/record.aspx